I have a betta about 2 yrs old. He keeps getting fin rot. He’s in a 5 gal tank. I do 25% water changes weekly. Cycled tank. No ammonia, no nitrites. pH a little high 7.5. I’ve been treating with Furan this time. Last time about 2 months ago emycin. Live plants. About 2” sand. Algae seems to like the environment and I wipe glass and wipe algae off plants with water changes. Any ideas why fin rot is so frequent?